The natural vitamin D-derived hormone, 1.alpha.,25-dihydroxy-vitamin D.sub.3, and its 25-deoxy analog, 1.alpha.-hydroxyvitamin D.sub.3, both exhibit high activity in vivo, being known as potent stimulators of the intestinal absorption of calcium and the mobilization of calcium from bone and as effective promoters of bone calcification. A very similar activity pattern is shown by 1.alpha.,25-dihydroxyvitamin D.sub.2 (U.S. Pat. No. 3,880,894) and its 25-deoxy analog, 1.alpha.-hydroxyvitamin D.sub.2 (U.S. Pat. No. 3,907,843). These compounds likewise elicit the full spectrum of vitamin D-type responses such as intestinal calcium transport, bone mineral mobilization and bone calcification response in the 1.alpha.-hydroxyvitamin D.sub.2 are characterized by having a C-24 stereochemistry as it occurs in the side chain of ergosterol, i.e. these compounds are defined by the structures shown below, where R represents side chains (a) and (b), respectively: ##STR1## More recently the C-24-epimer of 1.alpha.,25-dihydroxyvitamin D.sub.2 has been prepared and tested (U.S. Pat. Nos. 4,588,716 and 4,769,181). This compound is characterized by the structure shown above, where R represents side chain (c). Remarkably, this C-24-epimeric vitamin D derivative exhibits a distinctly different biological activity profile, in that it is active in stimulating intestinal calcium absorption and promoting the calcification of bone, but does not elicit a bone calcium mobilization response.